Mid-Infrared Spectroscopy and Chemical Sensing Technologies

Mid-infrared (MIR) spectroscopy exploits the 2.5–25 µm spectral window in which molecular vibrational and rotational transitions generate distinctive absorption features. By probing these intrinsic fingerprints, MIR techniques enable label-free identification and quantification of a wide range of chemical species in gases, liquids and solids. Advances in light sources, notably broadly tunable quantum cascade lasers (QCLs), and in photonic platforms such as semiconductor and diamond waveguides, have driven substantial improvements in sensitivity, spectral resolution and miniaturisation. Concurrent progress in functional coatings, microfluidics and data-processing algorithms has further extended the reach of MIR sensors into biomedical diagnostics, environmental monitoring, industrial process control and homeland security. Current challenges centre on enhancing the detection limits to trace-level analytes, integrating compact spectrometers into field-deployable devices and ensuring robust performance in complex matrices. Emerging approaches that harness microfabricated waveguides, evanescent-field geometries, novel transducer materials and artificial-intelligence-driven spectral analysis promise to realise next-generation chemical sensing platforms with unprecedented selectivity, throughput and portability.

Research from Nature Portfolio

Recent studies have provided essential refractive-index data for biological and aqueous samples in the MIR region, addressing a critical gap for optimisation of evanescent-field sensors. A comprehensive investigation of human whole blood and key clinical solutions established wavelength-dependent real and imaginary refractive indices across the MIR fingerprint region. The work introduced a generalised attenuated-total-reflection Fourier-transform approach that requires neither collimated nor polarised incident light, facilitating straightforward characterisation of aqueous media. These insights underpin the design of bedside and point-of-care biosensors by enabling precise modelling of light–matter interactions within thin-film and waveguide geometries to maximise sensitivity to biomolecular targets.

Mid-Infrared Spectroscopy and Chemical Sensing Technologies publication trend

The graph below shows the total number of articles in mid-infrared spectroscopy and chemical sensing technologies across all publications each year (not limited to Nature Index journals).

Technical terms

Mid-infrared (MIR) region: Wavelength range from 2.5 to 25 µm corresponding to fundamental molecular vibrations.

Attenuated Total Reflection (ATR): A sampling technique wherein an evanescent field at a high-index interface probes the adjacent medium.

Evanescent field spectroscopy: Detection of analytes via interaction with the decaying optical field extending from a waveguide or prism surface.

Quantum Cascade Laser (QCL): A semiconductor laser source emitting in the MIR, offering high power and narrow, tunable emission.

Waveguide: A microfabricated structure that confines and guides light, enhancing light–matter interaction over a defined path length.

References

1. Recent advances and trends in mid-infrared chem/bio sensors. TrAC Trends in Analytical Chemistry (2024).
2. Complex refractive index spectra of whole blood and aqueous solutions of anticoagulants, analgesics and buffers in the mid-infrared. Scientific Reports (2017).
3. Infrared spectroscopy based on broadly tunable quantum cascade lasers and polycrystalline diamond waveguides. Analyst (2018).
4. High sensitivity infrared spectroscopy with a diamond waveguide on aluminium nitride. Analyst (2021).
5. Mid-IR evanescent-field fiber sensor with enhanced sensitivity for volatile organic compounds. RSC Advances (2019).